Re: [Xen-devel] [PATCH v5 06/24] libxl: introduce vNUMA types

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Thu, 2015-02-12 at 19:44 +0000, Wei Liu wrote:
> A domain can contain several virtual NUMA nodes, hence we introduce an
> array in libxl_domain_build_info.
> 
> libxl_vnode_info contains the size of memory in that node, the distance
> from that node to every nodes, the underlying pnode and a bitmap of
> vcpus.
> 
> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> Cc: Elena Ufimtseva <ufimtseva@xxxxxxxxx>
> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
>
This looks fine, and matches what we agreed upon for this interface, a
few months back, so:

Reviewed-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>

Just one comment.

> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> index 02be466..14c7e7c 100644
> --- a/tools/libxl/libxl_types.idl
> +++ b/tools/libxl/libxl_types.idl
> @@ -356,6 +356,13 @@ libxl_domain_sched_params = 
> Struct("domain_sched_params",[
>      ("budget",       integer, {'init_val': 
> 'LIBXL_DOMAIN_SCHED_PARAM_BUDGET_DEFAULT'}),
>      ])
>  
> +libxl_vnode_info = Struct("vnode_info", [
> +    ("memkb", MemKB),
> +    ("distances", Array(uint32, "num_distances")), # distances from this 
> node to other nodes
> +    ("pnode", uint32), # physical node of this node
>
I am unsure whether we ever discussed this already or not (and sorry for
not recalling) but, in principle, one vnode can be mapped to more than
just one pnode.

Semantic would be that the memory of the vnode is somehow split (evenly,
by default, I would say) between the specified pnodes. So, pnode could
be a bitmap too (and be called "pnodes" :-) ), although we can put
checks in place that --for now-- it always have only one bit set.

Reasons might be that the user just wants it, or that there is not
enough (free) memory on just one pnode, but we still want to achieve
some locality.

This is probably something we can change/add later, but since it affects
the interface, I felt like saying it as soon as it came to my mind.

Regards,
Dario

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